Because of dwindling supplies of mineral hydrocarbon fuels, urgent social and economic needs exist for alternative fuels derived from renewable sources. Natural, biosynthetic oils, including virgin oils, typically those obtained from plant seeds or from other vegetable components or vegetable waste materials, represent a practical solution to the fuel supply problem. These natural fuels, except for processing and shipping expenditures, do not impact the availability of petrochemical fossil fuels.
Furthermore, with concerns of global warming, vegetable oil fuels are themselves carbon-neutral and upon combustion do not substantially increase the concentration of a green house gas or carbon dioxide, in the atmosphere. Vegetable oils are ultimately produced photosynthetically, utilizing atmospheric carbon dioxide as a carbon source. Hence, combustion of these oils essentially recycles carbon into the environment and does not increase the overall carbon burden. For practical purposes, it is critical, of course, that vegetable oil fuels are renewable, in contrast to petroleum fuels, which are in limited geological supply.
Waste vegetable oil (WVO) is an energy-rich resource obtained in large quantities as a byproduct from the food preparation industry, which employs vegetable oils as frying agents. One such common WVO is known, for instance, as yellow grease (YG) because of the color it develops upon use as a fry medium. Other spent frying oils or fats, such as beef tallow, derived from beef fat, and lard, derived from pork fat, are also potential fuels because of their high energy content. WVO, YG, lard, and spent tallow require recycling or further utilization to prevent build-up and environmental contamination. An increasingly attractive, economical usage for these waste products is as a fuel feedstock.
Biodiesel, already in active commerce, is one example of an alternative fuel utilizing vegetable oils, including WVO as a feedstock. Biodiesel is a renewable fuel produced by the transesterification of vegetable oils with a basic catalyst to produce combustible methyl and ethyl fatty acid esters. These esters are then separated from the reaction mixture to provide clean, energy-rich diesel fuel materials.
Typically, biodiesel fuels are blended with petroleum-based diesel fuels, such as Diesel Number 1 or Diesel Number 2, to produce hybrid fuels with acceptable performance and storage qualities (generic quality standards for diesel fuels are set by the American Society for Testing and Materials, ASTM; for diesel fuels that standard is ASTM D975). For example B20 is a hybrid biodiesel diesel fuel produced by blending 20% biodiesel with 80% petrochemical diesel by volume. Analogously, B50 biodiesel contains 50% biodiesel by volume.
B20 is a highly desirable diesel fuel, recently becoming more available commercially, with good cetane rating and other favorable characteristics. B20 contains less sulfur than Diesel Number 2, because the biofuel component is essentially sulfur free, and therefore B20 and other biodiesel hybrid mixtures burn more cleanly than Diesel Number 2 itself. B20 meets ASTM standard D6751, established specifically for biodiesel fuel quality and performance.
There are, nonetheless, drawbacks to biodiesel fuels. It is well recognized that the alcoholic components used in the manufacture of biodiesel, particularly methanol, are toxic and require special handling. These alcoholic components are volatile and highly flammable, and can be explosive. The reaction catalyst base, frequently sodium hydroxide, is also a highly corrosive and injurious substance that requires special containment and careful disposal. Glycerol, a relatively non-toxic byproduct of the transesterification reaction, requires storage and disposal. In addition, sludge and other deposits are formed in internal combustion engine systems that cause abnormal rise in carbon monoxide, unburned hydrocarbon concentrations in the exhausted gases, changes and delays in fuel flow. These result in deteriorated running performance, premature engine wear, and exhaust gas.
The current invention is a response to these and other deficiencies.